Hydrogen generating system



QWES WHEY-RENEE MMWW Emmi Dec. 31, 1968 BRATTON ET AL 3,419,361

HYDROGEN GENERATING SYSTEM Fil ed Nov. 15. 1965 INVENTORS Fem/ms A 84770, 1 /4390 .1: IeEV/IIULDJ 3,419,361 HYDROGEN GENERATING SYSTEM Francis H. Bijatton and Harold I. Reynolds, Northlie'd,

Minn., assiguors to G. T. Schjeldahl Company, Northfield, Minn., a corporation of Minnesota Filed Nov. 15, 1965, Ser. No. 507,748 9 Claims. (Cl. 23-281) The present invention relates generally to a method and apparatus for preparing hydrogen for use, for example, in a inflatant system and which may be used as a self-initiated, seli-sustainir g reactant system. fop prodgcipghydrogen. The system is adaptable for use in? inflating enclosures such as tethered or free floating balloon packages or the like, the system employing a controllable decomposing hydrogen liberating inflatant composition a which inflatant composition comprises a controllable selfsustaining reactant mixture of an endothermic and an exothermic compound.

Hydrogen gas may 'be used to inflate site markers; or other balloon' systems, and may be obtained from certain chemicals which readily release hydrogen upon contact with water or uponapplication of heat. For example, certaidliydrides, such as, for example, the alkaline earth hydrides yield hydrogen when placed in physical contact with water; however, these systems being sensitive to the presence of water are somewhat dangerous to handle, since the release of hydrogen may occur uncontrollably and may also occur relatively rapidly and prematurely. The byproducts of such a system are also generally dangerous or corrosive in nature. The system of the present invention utilizes a substantially anhydrous, nonaqueous, stable composition which may be heat activated to produce hydrogen. The system utilizes a unique combination of exothermically and endothermically reacting chemicals which may be blended and packaged to control reaction temperatures and produce nascent molec= ular hydrogen at near-ambient conditions. Hydrogen is also desirablefor use in connection with fuel cells and also have application for a wide variety of other purposes.

Briefly, according to the present invention the hydrogen generation or inflation system consists of a blend of reactants of hydrogen containing hydrogen liberating chemicals or compounds, one or more of these compounds being exothermically decomposable, along with one or more endothermically decomposable compounds; the arrangement being such thatthesdecompositionheats otreaction of the blend is seIflSustaining and controlled,

and the rapid evolution of hydrogen occurs at a relatively low temperature, this evolution occurring at a temperature substantially lower than the temperature obtained or reached for the decomposition of the exothermic material alone. Furthermore, a method of packaging these hydrogen-containing compounds is provided, I

the pagkaging rnethod beingssuchwthatwthe hydrogen is released controllably when the system is properly initiated'jdris'tiiiiulated. Generally the exothermically decomposable compounds selected for hydrogen gas ge er ation are selected from a group of preferably solid, pow-' dered, compactable materials, which are for example, the reaction products of hydrazine and borane. Also suitable as exothermically decomposable compounds are a solid and a, liquid.,material which are the reaction products of ammgpia and borane, The exothermic compounds take the generalized formula of R(R where R is selected from the group consisting of hydrazine, N H hydrazine, N H and ammonia NH;,; R is BH;,, and n is a positive integer between and 2. These com= pounds appear to be the only known self-sustaining hydrogen generating compounds which do not require nitcd States Patent 0 combination with aqueous solvents. The endothermically decomposable compound is preferably an alkali metal borohydride such as lithium borohydride.

When one or a mixture of the above suggested boranes, which decompose exothermically, are blended with an alkali metal borohydride, such as lithium borohydride, LiBH,, the net heat of reaction upon decomposition of the reactant mass is substantially less than the heat of reaction of the exothermically decomposing borane compounds alone. This occurs because the heat of reaction of the de compositionhof lithium bofiliydiidei isf Tendo- 'th inlnature. The decomposition of lithium borohydride requires a substained source of thermal energy which may be derived, for example, from the decomposition of an exothermically decomposable borane, for example hydrazine-bisborane.

By selecting a blend of certain specific molar ratios of the exothermically decomposable borane compounds utilized with the lithium borohydride, the net heat and rate of reaction of the blend can be varied and controlled. to certain predetermined levels. A recommended blend based generally upon a net heat of reaction of the decompositions of lithium borohydride and hydrazinebishorane would be 2 to 3 moles of LiBH, to one mole N H (BH In calculating overall temperature rise, of the system, one considers the heat capacity of the packaging materials which could be utilized, such as the enclosure for example and inert chemical byproducts of the reaction, the loss of heat due to the isothermal and 30 adiabatic expansion of the hydrogen and other gases present. It is concluded that the overall temperature rise above the ambient for the evolved hydrogen and for the entire system is. modest. Reactant blends or ratios of two moles of BER, and one mole of?N-,;H (BH have been successful with rapid cooling of the evolved hydrogen after leaving the reaction mass. If desired, initial ignition of theebler'ids may be accomfplished by a heat souree'sfich "as a resistance heater, fabelectrical squib, a mechanical squib, or open flame deordinary percussion caps iiiay be utilized if desired. Ordinary detonating devices ihay not initiate the reaction, since an elevated temperature in the range from about 250 C. to 300 C. is normally required to initiate the reaction for most blends. Also, in ord rto enhance the decomposition reaction, the blend may be graded to provide a more highly exothermically composition at the beginning portion than at the remainder of the material to be decomposed.

These hydrogen generating materials may be encapsulated or otherwise packaged in such a manner that they may be adapted as a convenient source of predetermined quantities of hydrogen for use in school or commercial laboratories, as well as for the inflation of lighter than air balloons or other inflatables. If desired, the materials can be properly blended in certain predetermined amounts, or may be mixed with certain binders to facilitate handling or specific reaction rates, and specific compression or extrusion operations may be utilized to form shapes to provide acceptance into predetermined container forms or the like. In one application of this invention, the material may be packaged within a tuburlar porous or otherwise gas permeable insulating material such as braided fiber glass, asbestos sleeve, high temperature porous open-cell synthetic foams. Lead alloy or plastic sheathing or the like may also be used in combination with these other porous materials, if desired. The encapsulated material may then be attached to the inner surface or wall of an inflatable structure such as a normal lighter-than-air balloon or the like fabricated from Mylar or other film rived from a torch, matchf candle or the like. In addition, I

ricated from Nichrome wire for example, Pyrofuse, an

material, or may be supported or contained in a suitable canister or container with inflation connections to the device to be inflated. This encapsulated material may also be suspendedfrom the inner film wall by means of a supporting web or the like, if desired. When provided with a suitable reaction initiating device, the hydrogen evolution may be obtained, as required.

Therefore, it is an object of the present invention to provide an improved hydrogen generating system which may be utilized to produce a hydrogen fill gas for an inflatable envelope or other structure.

It is yet a further object of the present invention to provide an improved technique and apparatus for providing a source of hydrogen which does not require the availability of water as a medium for generating the hydrogen.

It is yet a further object of the present invention to provide an improved apparatus and technique for conveniently generating hydrogen on a self-sustaining basis without creating excessively high temperatures in the reactant system.

It is still a further object of the present invention to provide an improved technique and apparatus capable of generating hydrogen at a rate and quantity which renders the system sufliciently light in weight so as to be selfbuoyant in nature.

Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification, appended claims, and accompanying drawings, wherein:

FIGURE 1 is a perspective view, of an inflatable structure after its inflation and release from a suitable canister device;

FIGURE 2 is a detail view, partially in vertical section, taken through the interior of the canister device illustrated in FIGURE 1, and showing hydrogen generating system and the inflatable member retained therein, the inflatable member being in collapsed form;

FIGURE 3 is a detail view, partially in section, showing a suitable detonating appartaus for initiating the decomposition reaction of a suitable blend of hydrogen generating materials provided and disposed in the canister device, and the detonating apparatus being partially actuated; and

FIGURE 4 is a detail elevation view, showing a short length of the hydrogen generating materials in tubular encapsulated form with the encapsulated and encapsulating material being partially broken away.

In accordance with the preferred modification of the present invention, the inflation system generally designated includes a canister enclosure or the like, the canister being fabricated from a pair of separable sections including a lower section 11 and an upper section 12. These sections are held or otherwise retained together by any suitable sealing means or the like, such as the hermetic tape bond or tear strip such as at 13. The canister section 1 1 and 12 may be fabricated from any suitable material, but preferably are fabricated from seamless round cylinders of high tensil material, a suitable material being high tensil chrome molybdenum steel,

In the interior of the canister, particularly in the confines of the upper portion 12, a balloon 15 is normally disposed in collapsed form. This ballon is shown schematically in collapsed disposition in the canister in FIG- URE 2, but is shown in inflated disposition in FIGURE 1. Obviously the balloon 15 may be folded directly upon itself, if appropriate for the particular inflatable being utilized. The manner of inflating the balloon structure 15 by means of the hydrogen generating system will'be provided in greater detail hereinafter.

With specific reference to FIGURE 2 of the drawings, the balloon 15 is coupled at its open end 16 to a hollow inflation plate member 17. This inflation plate 17 is provided with a tether line 18 coupled thereto, and is furthermore coupled to a hydrogen inflating tube 20. In

this regard, the tether line 18 is coupled at one of its ends to an eyelet member 21 secured to the inflatable balloon along plate 17, and at its other end to any eyelet or anchor member 22 secured to the canister frame. The inflation tube 20 is in communication with the interior of the balloon 15 through the inflation plate 17 and is also in communication with the hydrogen generating system generally designated 25. The hydrogen generating system 25 is confined within the enclosure cyllinder 26, this cylinder having appropriate tensile strength for resisting moderate pressures of confined hydrogen. A spitable filtering and cooling valve or member 27 provides commiiiiicatiorfbtween the hYdroEifg'iferating system 25 within the cylinder 26, and the inflation tube 20. Hydrogen is generated in this system in the manner as hereinafter set forth in detail.

While hydrogen can be generated in a variety of manners, such as by the chemical reaction between a metal and an acid, or by the reaction of water with a catalyzed metal'hydride, an anhydrous or dry system using materials which react by heat or thermal energy alone is clearly advantageous. Specifically in the preferred modification or aspect of the present invention, a controlled self-sustaining reaction is possible wherein a substantial quantity of hydrogen will be made available without requiring elaborate or excessive precautions, or unsual equipment.

The, hydrogen generating system generally designated 25 includes a hydrogen generating or liberating composition formed in tubular configuration and covered by a suitable sheath or the like. While tubular is herein employed in the description of the cylindrical tubular member 30, the term tubular as employed in this specification and claims is intended to incompass any geometrical configuration having any cross-sectional form including round, elliptical, square, rectangular and also other multisided configurations. With reference to FIG- URE 4, the hydrogen liberating composition is shown at 30, with the sheathing being shown in separate coaxially arranged layers, the inner layer being a low melting, such as forlexample antimony-lead alloy encasement, theouter layerbeingiaporous nature of the glass braid will permit the hydrogen gas to escape into the interior of the chamber 26' through filter 27 and through inflation tube 20 and thereby fill the balloon. It is not essential that the material be encapsulated, and as an alternative, pelletized shapes'in a variety of forms such as cylindrical, torroidal, cubical,--rectangular parallelopiped or the like may be employed.

Theicontrolled reaction of the hydrogen generating or liberating substance 30 can be initiated by a plurality of different techniques. For example, a mechanical squib such as shown in FIGURE 3 at may be utilized to establish initial ignition of the reactant system. Here, a percussion cap of a type which is now widely commercially available is shown at 36, and is struck by a rigid rriechanical ram 37 when ignition is desired. The ram 37 is preferably metallic in nature, and is retained in place by the combination of the locking ball 38 and the removable flexible pin member 29. The ,pin 29 retains the pre'compressed spring 40 in place within the tubular cylinder 41. Upon removal of the pin 39 by means of a pull on the lanyard 43, as illustrated partially performed in FIGURE 3, the coiled spring 40 may be permitted to exert ag shock force on the member 37. Of course, the initiating system 35 is sealed within the confines of the lower portion 11 of the canister, and lanyard 43 along with the exposed portion of the pin 39 is preferably recessed within the system and protected mechanically by means of a protective shield covering as at 45. Shield 45 is sealed in place by any suitable means, such as the tape or tear strip shown at 46. In its design aspects, the mechanical squib may be made resistant to various degrees of shock. For example, the apparatus disclosed in FIG- URE 3 may be readily and conveniently designed to be t BMh generating a ,snfisisnt quantity, Qtsn Absorbing the energy evolved from the hydrazine-bis borane decomposition to decompose LiBH should result in a net decrease in the reaction temperature and subsequent evolved H The extent of thermal decomposition of LiBH, is dependent upon the operating conditions in cluding time, temperature, and amount of each reactant. The LiBH decomposition is reported to proceed as follows:

resistant to a shock of 20 GS, which is sufficient to provide a wide margin of safety against accidental balloon inflation in the event the canister is dropped.

The enclosure 26 is preferably prepared in order that it may be flushed of any undesired atmosphere, and thereafter filled with a suitable inert or inactive atmosphere such as nitrogen or the like. For this purpose, a suitable inlet and outlet valve system as shown at 50 and 51 respectively, may be provided. When the apparatus is initially packed for use, the assembly is treated in order to provide such a suitable inert atmosphere within the confines of the enclosure 26.,

When ignition is desired for the reactive sublimation of the hydrogen generating material, the lanyard 43 is pulled and the rhember 37 is caused tp strike'jthepefciission mem- 1 Using the heats of formation of LiBH, and UP! as 46.4 kcal./mol and -21.6 koaL/mol, respectively, the absorption in the decomposition of LiBH would be 24.8 kcaljmol or 1.14 kcal./gram LiBH However, 5 these values are used cautiously because of the assumed products of decomposition, and because the LiBH, must be elevatedto a high temperature to achieve any practical rate of 'decomposition. (Very slow decomposition of LiBH, has been reported at 280 C. but higher tempera- 0 tures are required for a substantial, sustained extent of hydrogen release.) Since LiBH; has a fairly high specific heat, at least some heat will be absorbed in simply raising te $11 reaction .ofthe Hi 'Eii da material FillTThe balloon or other inflatable inember 15 which has previously been freed from the confines of the upper canister portion 12, is then filled by means of the controlled flow of hydrogen gas from the enclosure 26, the hydrogen passing through the inflation tube member 20, and ultimately into the confines of the balloon 15. The

h the temperature prior to decomposition. tether 1111-6 18 i. the inflated structure captlve In To determine the correct proportions of hydrazine-bisthe desired area 1f this 1s desirable.

Th h h 0 borane and.,LiBH in the gas generating mixture, it must 6 strllcmre as ilgmficant a vantages t at be recognized that (1) work will be done by the liberated rently available materials render the system self-buoyant gas to expand the balloon and (2) excess energy will m nature that i the weight of the Ieactmg material have to be maintained during decomposition of hydraerates a-sufficrent quantity of hydrogen to provide a buoyant effect exceeding the weight of the material being g z sgi w 3:25; i m ifi g i hi bz ll li ?:r eX- utilize? and consumed in theinfiatiqn Process ample of volume V or 6 cubic feet of 1.7 1 0 cubic yanous compoupds or blends l i i can be centimeters, is equal to fPdV, assuming adiabatic exutlllzed for producing hydrogen gas, this being in a dry pansion at vatmosplwric pressure Where anhydrous system, the compounds orblends of compounds being arranged to react controllably toward sublimation. 7 0 h i t f l n Hg at sea level, cm.,

Generally speaking, blends of materials can be utilized l3 6=density f Hg, y a

which will produce hydrogen by the initial application 980=acce1eration due to gravity, cmjsecfi of heat alone, the system being one in which the reaction 7 5 1 f 6 cubic ,f t balloon in e then;

is self-sustaining in nature. The endothermically decom- W=172 5X 9 dyne cm =1420 ca1ories posing material acts to absorb heat evolved from the decomposition of the exothermic reactant, and proper blends provide a controllable self-sustaining reaction rate to yield a continuous supply of reasonably cool hydrogen gas to the balloon or other inflatant system.

Assuming 2000 excess calories are normally required to maintain decomposition of LiBH in a hydrogen generating system, then to determine the proportions of hydrazine-'bisborane to LiBH, to yield a net heat of reaction of TABLE I Type Form Name Exothermie Solid, flydirazine-bis-boranm do. 0

Hydrazine-monobor 15. 4 Ammonia borane N 19.5 Diammoniate of ammonium NH4B3Hg(NH3)5.- 20.0

hydrotriborate. Endothermic Solid Lithium borohydride LiBH4 14.8

A mixture of hydrazine-bisbor ane, .as the exothermic 4120+2000 calories, the following exemplary calcularnaterial together with lithium borohydride as the endo-' tions are presented: thermic material is the preferred reactant blend for use -90B 24. =-6. in connection with the present invention although other Where 1+ 8L 12 (1) exothermic materials may be used instead of hydrazine- B=mo1 es of hydrazine bisborane and bis-borane. This composition contains a high weight-perof LiBHb cent of hydrogen, and the solid form lends itself-to convenient packaging or encapsulation. Each of the compounds in the reactant mixture decomposes substantially independently, and the only interdependence in the entire system is that of the lithium borohydride for its heat of decompositions energy obtained from the hydrazinebis(borane) decomposition.

The decomposition of the hydrazine-bisborane is reported to proceed as follows:

Using heats of formation of hydrazine-bisborane and boron nitride as 30 kcaL/mbl and 60 kcaL/mol, re Thus, 0195 mole of N H (B-H blended with 3.18 moles spectively, the complete decomposition of hydrazine-bisof LiBH, will decompose to liberate 6 cubic feet of hyborane or 1.51 kcal./ gram hydrazine-bisborane. drogen gas. Since 0.95 mole of hydrazine-bisborane equals -90=heat liberated by B in kcal./-rnol, 24.8=heat absorbed by L in kcaL/mol, -6.12=net heat of reaction in kcal.

5B+l.5L=9.5 (2) where: 5 and 1.5 =the moles of H produced per mole of B and L respectively and 9.5 moles of H required to produce 6 it. of H gas at estimated reaction efliciency of percent. 70 Solving (l) and (2):

L=3.l8 moles and 8: 0.95 mole 56.7 grams and 3.0 moles of 'LiBI-L, equals 69.4 grams the total weight W of chemicals will be 126.1 grams per unit. If. 0.90=approximate density of hydrazine-bisborane and O.66=approximate density of Li-BH the final density p of the chemical mixture in our hydrogen generator will be approximately 0.765/cc.

To determine the length of our linear hydrogen as depicted as 25 in FIGURE 2, it can be calculated from L=V /1rr. Since V=w/p=l66 cc. of chemicals and assuming a diameter, d=0.250 inch=0.6350 cm.; L=508 cm.=2-00 inches=l6.7 feet.

To estimate the increase in hydrogen gas temperature AT above ambient, consider the system in the initial state at high temperature and cool the system down to a low final temperature. In this cooling process 2000 calories are arbitrarily chosen as the amount of heat which needs to be extracted Over and above the work W of expansion. Hence:

where,

EC =total heat capacity of system, Mylar, C =4.l cal./deg., Hydrogen, C =36.8 cal./deg., Lead alloy, C =24.4 cal./deg., Glass, C =85.7 cal./deg., and AT,=13.2C increase over ambient,

neglecting heat capacity of residual chemicals and the effects of cooling due to transfer of heat to outside air.

It will be appreciated that the recommended hydrogen generating compositions, when properly blended in predetermined amounts to accommodate the conditions ex isting upon use. Furthermore these materials can be mixed together with certain diluents and/or inert binders such as powdered polystyrene, gelatin, or the like, in order to facilitate handling. These mixtures can then be subsequently compressed together, or extruded,-and containers provided therefore, the containers being such that the thermal energy required to raise their temperature is not sufficiently high so as to adversely affect the reaction rates concerned. It will be appreciated that as an alternative, an in-situ arrangement can be prepared utilizing a high temperature synthetic foam, which can he used to secure the reactants to the inner wall of a balloon film along with a suitable tape. The hydrogen liberating material may also be placed within a tube prepared from polyethylene, polyvinyl chloride, lead alloy sheath or the like, the tube then being suspended from the balloon wall by means of a support web such as Mylar or similar tape. In either system, the inflation arrangement would resemble a fuse cord or the like. A graded composition could be utilized, if desired, as previously pointed out.

If desired as an additional control or moderating effect on the hydrogen generation system, a quantity of pelletized metals, foraminacious metals, or the like may be utilized in combination with the hydrogen liberating composition. Preferably, metals with high thermal conductivity such as copper, aluminium or silver inlthe form of wires, whiskers, tiny pellets, powder or like forms may be employed. Thgfinelyedividedrnetal particlesw p vide the advantagesof heat t ianfifer -together with the mcderationof the rate of reaction, both of these contributing t6 the Stability of 'thereaction rate and consequently the stability of the system.

Example .l.-A 1:2 mole mixture of hydrazine-bisboraneand lithium =borohydride powders was made by gently stirring the materials together. This was then made into pellets by pressing to a shape approximately 15 mm. in diameter and 7 mm. thick. Four pellets, weighing approximately 5 grams were placed in a heavy Wall test tube approximately 2 centimeters in diameter and 90 centimeters long. A rubber stopper containing a 10 millimeter diameter glass tube was placed in the top of the test tube and through separate holes leads were made to a loop of nichrome wire which was placed in contact with the top pellet. The test tube was connected to Mylar spherical shaped balloon about 25.4 cm. diameter by a length of plasticized polyvinyl chloride tubing. The residual gas 5 in the system consisted of dry nitrogen. On completion of the assembly of the equipment the hydrogen discharge was initiated byWQQIl L SQQgjhB nichrome coil to a variable vol a on a l l Q-yoltline which permittedtlieZ'gradufl application of voltage to the system. As the nichrome -vvi'rie developed a red glow, a soft red glow developed in the pellets as the reaction occurred. The gas evolved carried with it fairly large quantities of very finely divided powder and filled the balloon to essentially its full size. From the position of the balloon after inflation, the presence of a gas lighter than air was indicated.

In other similar experiments conducted with the sys-- tem, opening of the balloon to the air lead to rapid reaction and buring of the flammable gas contained within the balloon. I

It will of course, be understood that various changes may be made in the form, details, arrangements and proportions of the parts without departing from the scope of our invention as set forth in the appended claims.

We claim:

1. Means for generating hydrogen upon application of heat to a self-sustaining reactant system comprising a .Lhermally reactant blend of controllably exothermically and endo th ermically. decomposable compounds, each being decomposable to liberate hydrogen gas and includ- 1m: r a

(a) an exothermically decomposable compound decomposable to liberate nascent hydrogen as a reaction product together witlil (b) an endothermically decomposable compound decomposable to liberate nascent hydrogen as a reactant product, the arrangement being such that said reactant blend decomposes at a predetermined controllable self-sustaining rate.

2. The hydrogen generating means as defined in claim 1 being particularly characterized in that:

(a) said reactant mixture is formed in tubular configuration, the tube having an axial length which is substantially greater than the cross-sectional dimen- SlOl'l.

3. The hydrogen generating system as set forth in claim 1 being particularly characterized in that:

(a) said exothermically decomposable compounds are selected from the group consisting of the reaction products of hydrazine and borane, and hydrazine and ammonia.

4. The hydrogen generating system as set forth in claim 3 being particularly characterized in that said exothermically decomposable compounds are selected from the group consisting of hydrazine-bisborane, hydrazine diborane, ammonia borane, and the diammoniate of ammonium hydrotriborate' 1 5. Infiatant meansfor inflating an inflatable structure with hydrogen comprising:

(a) a self-sustaining reactant mixture including an ex othermically decomposable compound decomposable to liberate hydrogen gas together with ap endo; thgrmjeallysublimating compound decomposable to liberate hydrogen;

(b) reaction enclosure means retaining a quantity of said reaction mixture in substantially continuous tubular form; a

(c) means for transmitting the hydrogen gas from said reaction enclosure to said inflatable structure.

70 6. The inflatant means as set forth in claim being particularly characterized in that:

(a) said reactant mixture is formed in tubular configuration, the tube having an axial length which is substantially greater than the cross-section dimensxon.

7. The inflatant means as set forth in claim 6 being the diammoniate of ammonium hydrotriborate, t0-

particularly characterized in that: gether with;

(a) ignition means are provided adjacent an axial end (b) and an endothermically decomposable compound portion of said tubular arrangement of said reactant decomposable to liberate hydrogen as a product of mixture for commencing the decomposition of said 5 decomposition. reactant mixture.

8. The inflatant means as set forth in claim 5 being References Cited particularly characterized in that: UNITED STATES PATENTS (a) a means are provided for moderating the rate of 2,389,448 11/1945 Mekler 23281 flow of hydrogen from said reactlon enclosure to 10 2,988,430 6/1961 Homer said inflatable structure. 9. Infiatant means for inflating an inflatable structure hydrogen gas Fl t MORRIS o. WOLK, Primary Examiner.

(a) a self-sustaining reactant mixture consisting essentially of. a mixture of exothermically decomposable 15 5ERWIN,ASSiSm"t Examinell compounds decomposable to liberate hydrogen gas Us Cl XR selected from the group consisting of hydrogen-bisborane, hydrogen-diborane, ammonia borane, and 23-211 3,323,873 6/1967 Horn et a1. 23-281 

1. MEANS FOR GENERATING HYDROGEN UPON APPLICATION OF HEAT TO A SELF-SUSTAINING REACTANT SYSTEM COMPRISING A THERMALLY REACTANT BLEND OF CONTROLLABLY EXOTHERMICALLY AND ENDOTHERMICALLY DECOMPOSABLE COMPOUNDS, EACH BEING DECOMPOSABLE TO LIBERATE HYDROGEN GAS AND INCLUDING: (A) AN EXOTHERMICALLY DECOMPOSABLE COMPOUND DECOMPOSABLE TO LIBERATE NASCENT HYDROGEN AS A REACTION PRODUCT TOGETHER WITH, (B) AN ENDOTHERMICALLY DECOMPOSABLE COMPOUND DECOMPOSABLE TO LIBERATE NASCENT HYDROGEN AS A REACTANT PRODUCT, THE ARRANGEMENT BEING SUCH THAT SAID REACTANT BLEND DECOMPOSES AT A PREDETERMINED CONTROLLABLE SELF-SUSTAINING RATE. 